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title: Introduction to Helm
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# <center><i class="fa fa-book"></i> Introduction to Helm </center>

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###### tags: `study` `Kubernetes`


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**🎯 Goals:**
- [x] - <a href="#12-Helm-Architecture">To know Helm Architecture</a>
- [x] - <a href="#Module-2-Basic-concept">To know the basic concept</a>
- [x] - <a href="#Module-4-Summary">Summary </a>
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:::info
:bookmark: **Reference:**
- [A more detailed comparison of Helm 3 and Helm 2](https://jakubstransky.com/2021/06/15/kubernetes-helm-operational-models/)
- [Delet Namespace](https://phoenixnap.com/kb/helm-delete-deployment-namespace)
---
:link: **++Links++ to my notes on the same topic**
- [](/@MingHung/Docker) &emsp;&emsp; [](/@MingHung/Kubernetes)
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[toc]
# Module 1: Introduce

## 1.1 What is Helm
- Helm is a suite for ==managing Kubernetes== applications.
- Through the Helm Charts system, developers can package, install, and upgrade related Kubernetes applications. For these profiles:
- Version control
- Manage
- Update
- Effectively manage various versions of ==Yaml files==.

## 1.2 Helm Architecture
### 1.2.1 Class relationship

<!--

digraph Kubernetes {
    rankdir = LR
    nodesep = 1.0 // increases the separation between nodes
    node [color=black,fontname="微軟正黑體",shape=box, style="rounded,filled", fillcolor=gray] //All nodes will this shape and colour
    edge [color=black, style=dashed] //All the lines look like this
    Namespace->Chart
    Chart->Release
}

-->

# Module 2: Basic concept
## 2.1 Main function (command)
### 2.1.1 List Helm
- List Helm deployments in the **current namespace** with:

helm list

- List Helm deployments all namespace with: (or select)

helm list --all-namespaces
helm list --namespace <namespace_name>
kubectl get namespace

- search Helm by keyword

helm search repo <KEY WORD>

### 2.1.2 Delete
1. Delete All helm
2. There is no method to remove **namespace** when **deleting a release** using Helm commands. So using the **kubectl** command.

helm delete peddling-hog
kubectl delete <namespace name>

## 2.2 OverView
- Helm collectively refers to **++all++ Kubernetes applications (yaml)** as ==Charts==.
- Helm's tool will **package these ++charts++** into ==tgz files==
- For **applications installed into Kubernetes**, Helm calls it a ==Release (released object)==.


### 2.2.1 Chart in v2
- **Chart Architecture**
- `Chart.yaml`: Defines the Metadata of this Chart, including the Chart's version, name, description, etc.
- `charts`: Folder. Put other Charts, called SubCharts.
- `templates`: Defines the Kubernetes components required by this Chart service.
(However, the parameters of each component will not be written in it, but will be substituted in the form of parameters.)
- `values.yaml`: Define all parameters of this Chart, which will be substituted into the elements in templates.


### 2.2.1 Chart in v3
- **Chart Architecture**

## 2.3 Customized
- Helm uses ==Go Template== to customize **Yaml**
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- Example Yaml:

apiVersion: v1
kind: Service
metadata:
  name: {{ include "example.fullname" . }}
  labels:
{{ include "example.labels" . | indent 4 }}
spec:
  type: {{ .Values.service.type }}
  ports:
    - port: {{ .Values.service.port }}
      targetPort: http
      protocol: TCP
      name: http
  selector:
    app.kubernetes.io/name: {{ include "example.name" . }}
    app.kubernetes.io/instance: {{ .Release.Name }}

- Use a large number of **`{{}}`** formats for variable substitution
- Can make **Yaml** very **flexible**
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# Module 3: Comparison

## 3.1 Helm v2 v.s Helm v3
- **In v2 architecture**
- **v3 architecture is lightweight (compared to v2)**

## 3.2 Helm 3 main differences
### 3.2.1 **v3 Remove Tiller**
> Tiller server is used to communicate with API server and use chart to build services on k8s cluster
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**v3 will eliminate the need to manage complex application releases in a shared cluster**
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With Tiller gone, the security model for Helm is radically **simplified**.
Helm 3 now supports all the modern **security**, **identity**, and **authorization** features of modern Kubernetes.
- **Cluster administrators can restrict user permissions at whatever granularity they see fit.**
> Helm's permissions are evaluated using your kubeconfig file.

### 3.2.2
The related apiVersion in the Helm Chart needs to **jump** from v1 to v2 to declare that the Helm Chart belongs to Helm v3.

### 3.2.3
**v3** uses a three-way comparison for testing, which will use the `past state`, `current operating state` and `expected state` to **compare**, and finally generate updated content.
### 3.2.4
With the support of **OCI**, the packaged format of Helm Chart in the future can follow the format of OCI (Open Contaianer Initiative).
# Module 4: Summary
The package manager for **Kubernetes**;
Helm is the best way to **find, share, and use software built** for Kubernetes.

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